Electrical interlock means



Aug. 0, 1968 J. B. CATALDO ETAL 3,398,329

ELECTRICAL INTERLOCK MEANS Filed Nov. 1, 1965 5 Sheets-Sheet l I JNVENTORS JdA A a. 6/7774/00 Aug. 20, 1968 J. B. CATALDO ETAL 3,398,329

ELECTRICAL INTERLOCK MEANS Filed Nov. 1, 1965 5 Sheets-Sheet 3 km I WV U 0, 1968 J. B. CATALDO ETAL 3,398,329

ELECTRICAL INTERLOCK MEANS Filed Nov. 1, 1965 5 Sheets-Sheet 4 STOP CONTROLS 0, 1968 J. B.CATALDO ETAL 3,398,329

ELECTRI CAL INT ERLOCK MEANS Filed Nov. 1, 1965 5 Sheets-Sheet 5 United States Patent ELECTRICAL INTERLOCK MEANS I John B. Cataldo, Bloomfield Hills, and Frank W. 'Kussy, Birmingham, Mich., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Nov. 1, 1965, Ser. No. 505,899

13 Claims. (Cl. 317-136) This invention relates to electromagnetic contactors in general and more particularly relates to novel arrangernents for electrically interlocking two such contactors so only one of them is actuated at any given time. I

The I. B. Cataldo et a1. copending application Ser. No. 189,915, filed Apr. 24, 1962 entitled, Electrical Device, now"U.S. Patent No. 3,324,431 and assigned to the assi-gnee of the instant invention describes in detail the construction of an electromagnetic contactor as well as accessories therefor arranged in combination to form a motor starter. For control of reversible or two speed motors two contactors are used with these contactors having their controls interlocked, either electrically or mechanically, so that only one of the contactors is actuated, or pulled in, at any given time. The instant invention is concerned exclusively with electrically interlocked contactors.

Considering the application in question to be one for control of a reversible'motor, by utilizing the teachings of the instant invention four different modes of operation may be achieved through minimal number of different control elements and wiring. These modes of operation are (1) stop before reverse with local controls only, (2) stop before reverse with local controls and remote controls, (3) reverse without stopping with local controls only, and (4) reverse before stopping with local controls and remote controls.

As set forth in detail in the aforesaid copending application Ser. No. 189,915, now US. Patent No. 3,324,- 431 an electro-magnetic contactor includes a plurality of main contacts simultaneously operable upon energization of the operating coil of an electromagnet. The energizing circuit for the operating coil includes a normally open and a normally closed switch combined into a unit customarily designated as a holding interlock. The normally open switch is manually operated to closed position and is held closed through the actuation of the operating coil. Thereafter, when the normally closed switch is momentarily operated to its open position the operating coil is deenergized and the normally open contacts move to open position. v

1 In the instant invention both contacts of the holding interlock are maintained in actuated position by the energization of the electro-magnet operating coil. As will be hereinafter explained in detail, by utilizing such a construction and by utilizing appropriate wiring a pair of electromagnetic contactors may be interlocked in a novel manner.

In the prior art the wiring required for each of the four operational modes heretofore described was vastly different in each case so that essentially all wiring had to be done in the field where the likelihood of making errors is much greater than in the factory. Further, where the contactors were mounted within an enclosure and operated by push button means mounted to the enclosure cover it was necessary to make wiring connections directly to the cover mounted switches.

' 1 As will be hereinafter explained the instantinvention provides'a very flexible apparatus in that a major portion of the wiring'for all four operational modes is identical and very little wiring need be done in the field. Further, the cover mounted push buttons are purely mechan- 3,398,329 Patented Aug. 20, 1968 ical units so that it is not necessary to make any electrical connections to the movable cover.

Accordingly a primary object of the instant invention is to provide novel means for electrically interlocking a pair of electramagnetic contactors.

Another Object is to provide a novel arrangement for electrically inter-locking magnetic contactors such that very little field wiring is required in order to achieve any one of a number of different operational modes.

Still another object is to provide novel electrical interlock means for a pair of contactors mounted within an enclosure and operated by cover mounted mechanical switches A further object is to provide electrically interlocked electromagnetic contactors which operate both the normally open and normally closed contacts of the holding interlocks mounted thereto.

These as well as other objects of the instant invention will become readily apparent after reading the following description of the accompanying drawings in which:

FIGURE 1 is a schematic illustrating means utilizing the teachings of the instant invention to produce an electrically interlocked pair of electromagnetic contactors which need not be operated to stop position before reversing and are operable only by local controls.

'FIGURE 2 is a plan view showing the contactors and holding interlocks of FIGURE I mounted within an enclosure whose openable cover has been removed.

FIGURE 3 is a partial cross-section taken through line 3-3 of FIGURE 2 looking in the direction of arrows 3-3. In order to avoid confusion the electromagnetic contactors of FIGURE 2 are not shown in FIGURE 3. However, the enclosure cover is shown in FIGURE 3.

FIGURE 4 is a front elevation of one of the interlock units of FIGURE 3 with the cover thereof removed to reveal the contact structure.

FIGURE 5 is the plan view of the interlock unit of FIGURE 4.

FIGURE 6 is a partial side elevation of the interlock unit of FIGURE 5 looking in the direction of arrows 66 of FIGURE 5.

FIGURE 7 is an electrical schematic showing a modification of FIGURE 1 also including remote controls.

FIGURE 8 is an electrical schematic showing how the teachings of the instant invention are utilized to construct electrically interlocked contactors which must be stopped before reversing takes place and are only provided with local controls.

FIGURE 9 is an electrical schematic showing a modification of FIGURE 8 also including remote control.

Now referring to the figures and more particularly to FIGURES 1 through 6.. Electromagnetic contactor 11 includes three normally open main contacts 12a, 12b, which are simultaneously operated to closed position when the electromagnet operating coil 14 is energized. Electromagnetic contactor 15 includes normally open main contacts 16a, 16b, which are simultaneously operated to closed position when electromagnet operating coil 17 is energized. The windings of motor M are delta connected to terminals 18, 19, 20 with motor M being energized by three phase source 21 having terminals A, B and C.

Contacts 12a are in the line connecting terminals A and 20, contacts 12b are in the line connecting terminals B and 18, contacts 120 are in the line connecting terminals C and 19, contacts 16a are in the line connecting terminals A and 19, contacts 1617 are in the line connecting terminals B and 18, and contacts 160 are in the line connecting terminals C and 20. Thus, it is seen that when contactor 11 is energized motor M will rotate in what will hereinafter be called the forward direction F and when contactor 15 is energized motor M will rotate in the reverse direction R.

As best seen in FIGURE 2 electromagnetic contactors 11 and 15 are mounted side by side within enclosure 22 having an openable cover 23 (FIGURE 3) pivotally mounted at hinges 24. Holding interlock units 25, 26 are mechanically mounted to contactors 11 and 15, respectively, in the same manner shown in the aforesaid copending application Ser. No. 189,915. The contacts at the left of holding interlock unit 25 are normally open and the contacts at the left of holding interlock 26 are normally closed while the contacts at the right of interlock 25 are normally closed and the contacts at the right of interlock 26 are normally open.

Details of holding interlock unit 26 are best seen in FIGURES 4 through 6. More particularly, interlock unit 26 includes molded insulating base 27 having suitable internal formations formed in the front surface 28 thereof for operatively positioning the movable elements of interlock 26. Insulating front cover sheet 29, secured to base 27 by screws 29, retains the movable elements mounted to base 27. I

The normally open contacts at the right of interlock 26 include spaced stationary contacts 31, 32 disposed within base 27 and mounted to terminals 31a, 32a, respectively, extending through cover sheet 29. Bridging contacts 33 mounted to insulating plunger 24 is movable into engagement with stationary contacts 31, 32. Coil spring 35 biases contact 33 downward into engagement with ledge 34a of plunger 34 and also furnishes contact pressure when contact 33 engages contacts 31, 32. When contact 33 is in the open position shown in FIGURE'4, coil spring 36 biases contact 33 toward open position.

The normally closed contacts at the left of holding interlock 26 include stationary contacts 37, 38 mounted to terminals 37a, 38a which extend through cover sheet 29.

Bridging contact 39, extending transversely through elongated plunger 40, is normally engaged with contacts 37, 38 being biased to this position by main spring 41 and auxiliary spring 42. Spring 41 biases plunger 40 upwardly with respect to FIGURE 4 with this upward movement being limited by cooperating formations (not shown) on plunger 40 and base 27. Spring 42 is provided to compensate for overtravel of plunger 40 and is in engagement with the lower surface of bridging contact 39 and the upper surface of a ledge 43 at the lower end of plunger 40.

L-shaped brackets 44 have their vertical legs secured to opposite ends of base 27. The outwardly extending horizontal legs of brackets 44 are provided with clearance apertures 45 which receive screws 46 (FIGURE 2) for mechanical securement of interlock 26 to contactor 15.

The contactor illustrated in the aforesaid copending application Ser. No. 189,915 is provided with a movable carrier which carries the main bridging contacts and extending from this carrier is a single projection which engages the plunger for actuating the normally open contacts of the holding interlock to maintain these contacts closed when the electromagnet is energized. Contactor 15 of the instant invention includes such a projection 47 and in addition includes projection 48 extending from the movable contact carrier of contactor 15 so as to engage plunger 40 of the normally closed contacts to maintain these contacts open when coil 17 is energized. The upper portion of base 27 to the rear of plungers 34 and 40 is provided with cut-outs 47a, 48a which provide clearances for the movement of projections 47, 48 respectively. In-

- terlock 25 is of substantially identical construction to interlock 26 except thatthe normally open contact of interlock 25 is to the left of the normally closed contacts thereof with, respect to FIGURE 3, while the normally closed contacts of interlock 26 are to the left of the normally open contacts thereof.

. Conductor 51 connects stationary contact 31 to normally open contact 61 of interlock 25. Conductor 52 connects contact 37 to the other normally open contact 62 of interlock 25. Conductor 53 connects 38 to one side of operating coil 14 of contactor 11. Conductor 54 con,- nects contact 32 directly to normally closed contact 64 of interlock 25. Conductor 55 connects one end of operating coil 17 to the other normally closed contact 65 of interlock 25. Control poweris introduced at terminals L-l and L-2 with the former being connected to contact 61' and the latter being c'onected to the other terminals of both coils 14 and 17. v

As best seen in FIGURES 1 and 3, plungers67, 681c0nnected to bridging contactsp63, 66, respectively, for the normally open and normally closed contacts of interlock unit 25 are positioned so as to be engageable by bar 71. Plungers 34 and 40 are positioned so as to be engageable by bar 72 and another bar 73 is positioned so as to be engageable with both plungers 40 and 68. Bars 71, 72, 73 are mounted to the portions of push button controls 74, 75, 76, respectively, positioned on the interior side of enclosure cover 23. Since push button controls of this type are well known to the art no further descriptionthereof will be given, although it is noted that these push button controls are of the type illustrated in the F. W. Kussy et al. copending application Ser. No. 421,567 filed Dec. 28, 1964, entitled, Push Button Operated Criss-Cross Actuators, and assigned to the assignee of the instant invention.

Operation of the apparatus hereinbefore described takes place in the following manner. Starting with the condition in which the interlock contacts are in their normal conditions motor M is deenergized since both contactors 11 and .15 are open. That is, the energizing circuit for operating coil 14 is deenergized since normally open contacts 61, 62 are not bridged by contact 63 and the energizing circuit for operating coil 17 is deenergized since normally open contacts 31, 32 are not bridged by contact 33. By depressing forward control 74, bar 71 engages both plungers 67 and 68 thereby closing the normally open contacts of interlock 25 and opening the normally closed contacts thereof. Now the energizing circuit for operating coil 14 is completed as follows: L-l, 61, 63, 62, 52, 37, 39, 38, coil 14 and L-2. Energization of operating coil 14 pulls in contactor 11 to energize motor M for forward rotation and brings the contact carrier extensions 47', 48 of contactor 11 into holding position so that when forward push button control 74 is released plungers 67, 68 will remain depressed.

If stop push button control 76 is now depressed, bar 73 engages plungers 68 and 40. Now the normally closed contacts 37, 38, 39 of interlock 26 are open thereby interrupting the energizing circuit for operating coil 14. Since the normally closed contacts 64, 65, 66 of interlock-25 are also open at this time the energizing circuit for coil 17 is open. Thus, the energizing circuits for both coils 14 and 17 are open so that contactors 11 and 15 return to their;i normally open positions wherein motor M is deenergize If, instead of depressing stop push button control 76, reverse push button control 75 is depressed at a time when contactor 11 is energized, bar 72 engages plungers 34 and 40. This opens normally closed contacts 37, 38, 39 to interrupt the energizing circuit for operating coil 14 thereby opening contactor-11 so that projections 47', 48 thereof release plungers 67 and 68. Now a complete energizing circuit for operating coil 17 exists as follows: L-l, '51, 31, 33, 32, 54, 64, 66, 65, 55, coil 17 and L-2. If stop push button control 76 is now operated the conditions previously described in connection with the operation of control 76 will take place.

If forward control 74 is operated at a time when contactor 15 is energized, normally closed contacts 64, 65, 66 are opened thereby deenergizing coil 17. Contactor 15 moves to its open position so that extension 47, 48 release plungers 34, 40 and the energizing circuit for operating coil 14 is again established so that motor M is energized for rotation in the forward direction.

FIGURE 7 is an electrical schematic showing the addition of remote controls for achieving the mode of operation described in connection with the embodiment of FIG- URE 1. In the physical embodiment for FIGURE 7 the same contactors, holding interlocks and cover mounted controls shown in FIGURES 2 and 3 are utilized in the same relative positions illustrated in FIGURES 2- and 3. Since so much of the circuitry of FIGURE 7 is identical to the circuitry of FIGURE 1 like elements in both figures are identified by the same reference numerals and only the differences betweenFIGURES 1 and 7 will now be described.

More particularly, the direct connection between terminal 'L-l and contact 61 in FIGURE 1 is not found in FIGURE 7. Instead, in FIGURE 7 L-l is connected to one side of the normally closed stop control switch 81 whose other side is connected to one of the normally closed contacts 82 of the remote forward switch as well as to one of the normally closed contacts '86 of the remote reverse switch. The other normally closed contact 83 of the remote forward switch is connected to one of the normally open contacts 89 of the remote reverse switch while the other normally closed contact 87 of the remote reverse switch is connected to one of the normally open contacts 85 of the remote forward switch. The other normally open contact 84 of the remote forward switch is connected to contact 62 while the other normally open contact 88 of the remote reverse switch is connected to contact 32. In addition, contact 87 is connected directly to contact 61. As seen in the schematic of FIGURE 7 both the forward and reverse remote switches are double throw units with the bridging contact 91 of the remote forward switch normally engaging contacts 82, 83 and operable out of engagement with these contacts into engagement with contacts 84, 85. Similarly, bridging contact 92 of the remote reverse switch is normally in engagement with contacts 86, 87 and when operated out of engagement therewith is operated into engagement with contacts 88, 89.

Thus, it is seen that normally line terminal L-l is connected to terminal 61 through remote stop switch 81 when the normally closed contacts of remote forward and reverse switches. Obviously when remote stop switch 81 is operated the circuit between line terminal L-1 and the remaining elements shown in FIGURE 7 .is broken so that whichever of the contactors 11, may be energized at the time, such contactor will be deenergized and motor M will stop.

If neither of the contactors 11 nor 15 is energized the operation of the remote forward switch causes bridging contact 91 to engage normally open contacts 84, 85 thereby completing an energizing circuit for coil 14. This circuit consists of L-l, 81, 86, 92, 87, 85, 91, 84, 62, 52,

37, 39, 38, 53, coil 14 and L-2. When contactor 11 pulls in extensions 47', 48' thereof depress plungers 67, 68. Now the energizing circuit for operating coil 14 extends through elements L-1, 81, 82, 86, 92, 87, 61, 63, 62, 52, 37, 39, 38, coil 14 and L2. Thus it is seen that after contactor 11 pulls in contacts 84, 85 need not be bridged in order to maintain coil 14 energized. Accordingly, upon release of the remote forward control, coil 14 remains energized.

Thereafter, if the remote reverse control is operated bridging contact 92 is brought into engagement with contacts 88, 89 to interrupt the energizing circuit for operating coil 14 and establish an energizing circuit for operating coil 17. More particularly, when the remote reverse control is operated the normally open contacts 84, 85 are open and the normally closed contacts 86, 87 are open thereby interrupting the energizing circuit existing at thistime for coil 17, such circuit consisting or elements L-1, 81, 82. 91, 83, 89, 92, 88, 32, 64, 68, 65, 55, coil .17 and L-2. Naturally, the local controls 74, 75, 76 function in the manner previously described in connection with FIGURE 1.

In the embodiment illustrated in FIGURE 8 the stop control button 101 must be operated in order to reverse the rotation of motor M as distinguished from the ern- 'bodiments of FIGURES 1 and 7'in which motor rotation can be reversed merely by operating the forward or reverse controls, the stop control of FIGURES 1 and 7 being used exclusively for stopping the motor M.

The contactors, holding interlocks and electrical connections between the holding interlocks and contact operating coils are the same for both the embodiments of FIGURES 1 and 8 so that the same'reference numerals are applied to like elements in both figures and no additional description of the electrical inter-connections is given herein. Stop control 101, forward control 102 "and reverse control 103 are local controls. That is, they are mounted to the enclosure wherein contactors 11 and 15 are mounted. Operation of forward control .102 is effective to operate only plunger 57 while operation of reverse control 103 is effective to operate onlyplunger 34 while the operation of stop control 101 is etfective't operate only plunger 40 and 68.

It is seen that when stop control 101 is operated bridging contact .66 parts from contacts 64, 65 thereby placing a gap in the energizing circuit for coil '17 and bridging contacts 39 separates from contacts 37, 38 thereby placing a gap in the energizing circuit for coil 14. Thus neither coil '14 nor 17 can be'energized when stop control 101 is operated. When forward control 102 is operated bridging contact 63 engages contacts 61, 62. This provides an energizing circuit for coil .14 consisting of elements L-1, 61, 63, 62', 52, 37, 39, 38, 63, coil 14 and L2. When contactor 11 pulls in, bridging contact 63 is held in the closed position and bridging contact 66 is operated to the open position.

If at this time reverse control 103 is operated to bring bridging contact 33 into engagement with contacts 31, 32 coil 17 will not be energized since contact 66 is separated from contacts 64, 65. Similarly, with both contactors 11 and 15 deenergized operation of reverse control .103 brings bridging contact 33 into engagement with contacts 31, 32 thereby providing an energizing circuit for coil 17 consisting of elements L1, 51, 31, 33, 32, 54, 64, 66, 65, 55, coil 17 and L-2. When contactor 15 pulls in bridging contact 33 is maintained in engagement with contacts 31, 32 and bridging contact 39 is separated from contacts 37, 38. Thus, operation of forward control 102 will have no effect until stop control 101 is first operated. That is, operation of forward control 102 at a time when contactor 15 is pulled in will bring bridging contact 63 into engagement with contacts 61, 62. However, since bridging contact 39 is separated from contacts 37, 38 there is a gap in the energizing circuit for coil 14 so that contactor 11 will not pull in.

In the embodiment of FIGURE 9 the stop control must be operated in order to reverse the direction of motor rotation. Whether the operation takes place through the local or remote controls. The remote stop control is a normally closed switch 111, the remote forward control is a normally open switch 112 and the remote reverse control is a normally open switch 113. In the embodiment of FIGURE 9 line terminal L-1 is connected through switch 11.1 to terminal 121 of switch 112 which is connected directly to contact 61 as well as to contact 123 of remote reverse switch 113. The other terminal 122 of switch 112 is connected to terminal 62 while the other terminal 124 of switch 113 is connected to contact 32. The other elements of FIGURE 9 bear the same reference numerals as corresponding elements shownun FIGURES 1, 7 and 8 and have the same electrical lnter-connection so that no additional description thereof will be given herein.

Operation of the embodiment of FIGURE 9 takes place in the following manner. When the sto control switch'lll is operated the line connected directly to energizing terminal L-1 is interrupted so that neither coils 14 nor 17 may be energized regardless of the operation of local controls 102 and 103 or remote controls 112 and 113. Remote forward switch 112 parallels the normally open 7 switch of holding interlock 25 so that when switch 112 is closed coil 14 is energized and contactor 11 pulls in to close the normally open section of interlock 25 and open the normally closed section thereof. With contactor 11 pulled in operation of remote reverse control switch 113 will have no effect since the normally closed contacts of interlock 25 are maintained in the open position by extension 47'.

With both contactors 11 and 15 deenergized'operation of remote reverse control switch 113 completes an energizing circuit for coil 17 thereby pulling in contactor 15 to close the normally open contacts of holding interlock 26 and open the normally closed contacts thereof. Thus, with contactor 15 pulled in, operation of local forward control 102 or remote forward control switch 112 will not energize coil 14 since the normally closed contacts of holding interlock 26 are open.

It is noted that bars 71 and 72 of FIGURE l are mounted eccentrically with respect to their respective controls 74, 75 by removable fasteners 71a, 72a, respectively. Further, each of said bars 71, 72 may be selectvely moved to another by rotation of 180 about its respective fastener 71a, 72a. In its said another position, bar 71 only engages plunger 67 when control 74 is actuated. Similarly, in its said another position, bar 72 only engages plunger 34 when control 75 is actuated. Thus, it is seen that when bars 71, 72 are rotated 180 from their positions of FIGURE 1 the components of FIGURE 1 now function in the same manner as the components of FIGURE 8 thereby interlocking contactors 11, 15 in a manner such that the stop control must be actuated before reversing takes place.

It is noted that in all four of the embodiments hereinbefore described the enclosure, the contactors, the holding interlocks and the connection points for conductors 51, 52, 53, 54 and 55 as well as these conductors are identical and all of these elements are mounted in the very same physical positions for all four embodiments. This is the item stocked by the supplier as a standard unit. When the contractor decides the type of operational mode required by the customer it is a simple matter to install the desired mechanical push button controls as required.

In the alternative, the stock item may include push button controls and bus bars 71, 72, 73 with bars 71 and 72 being positioned in the field to obtain the desired operational mode.

It should now be apparent that both interlock units may be identical. If this is the case naturally diflferently shaped push button operated bars must be provided in order to achieve the desired modes of operation hereinbefore described.

The provision of this standard unit minimizes field work thereby minimizing the likelihood of costly errors. This standard unit provides a convenient means for electrically interlocking a pair of electro-magnetic contactors to insure that only one of these contactors is energized or pulled in at any given time and this interlocking feature is provided for all four of the usual operational modes required.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exelusive privilege or property is claimed are defined as follows.

1. A combination including a first and a second electromagnetic contactor having a first and a second ope-rating coil, respectively; electrical interlock means for preventing both of said coils from being energized at the same time; said interlock means comprising a first and a second normally open switch; a third and a fourth norm-ally closed switch; means operating said first and said third switches to closed and opened positions, respectively,

when said first coil is energized; means'o'perating said second and fourth switches to closed and open positions, respectively, when said second coil is energized; a first energizing circuit for said coil including said first coil, said first and said fourth switches connected in electrical series,'with each other; and a second energizing circuit for said second coil including said second coil, said second and said third switches connected in electrical series with each other.'

2. A combination'as 'in claim 1 also including an enclosure wherein said contactors and said switches are mounted; control means for mechanically operating said switches; said control means having portions thereof accessible for manual operation from outside said enclosure.

3. A combination as in claim 2 in which said enclosure includes an openable cover; said control means mounted tosaid cover. I

f4. A combination as in claim 1 also includingcontrol means for mechanically operating said switches.

5. A combination as in claim 4 in which said control means includes a first, a second and a third control; said first control when actuated mechanically operating said first and said third switches to closed and open positions, respectively; said second control when actuated mechanically operating said second and said fourth switches to closed and open positions, respectively; said third control when actuated mechanically operating both said third and fourth switches to open positions.

6. A combination as in claim 5 also including a first, a second and a third remote control; said first remote control comprising a fifth normally closed switch connected in electrical series with each said energizing circuits; said second remote control including first normally open and a third normally closed switch section; said third remote control including a second normally open switch section and a fourth normally closed switch section; a first additional energizing circuit for said first coil including said first and said fourth switch sections, said fourth switch and said first coil all connected in series; a second additional energizing circuit for said second coil including said second and said third switch sections, said third switch and said second coil all connected in series.

7. A combination as in claim 5 also including an enclosure 'wherein said contactors and said switches are mounted; said controls having portions thereof accessible for manual operation from outside said enclosure.

8. A combination as in claim 7 in which said enclosure includes an openable cove-r; said controls mounted to said cover.

9. A combination as in claim 4 in which said control means include a first, a second and a third control; said first control when actuated mechanically operating said first switch to closed position without operating the remainder of said switches; said second'control when actuated mechanically operating said second switch to closed position without operating the remainder of said switches; said third control when actuated mechanically operating both said third and fourth switches to open positions.

10. A combination as in claimv 9 also indicating a first, a second and a third remote control; said first remote control comprising a normally closed fifth switch connected in electrical series with each of said energizing circuits; said second and said third remote controls comprising a normally open sixth and a normally open seventh switch .respectively; said first and said sixth switches connected in parallel; said second and said seventh switches connected in parallel.

11. A combination as in claim 9 also including an enclosure wherein said contactors and said switches are mounted; said controls having portions thereof accessible for manual operation from outside said enclosure.

12. A combination as in claim 11 in which said enclosure includes an openable cover; said controls mounted to said-cover.

13. A combination as in claim 4 in which said control means includes a first, a second and a third control; said first control including a first element selectively mountable in a first and a second position; when said first control is actuated said first element in said first position engaging said first switch and mechanically operating the latter to closed position without operating the remainder of said switches; when said first control is actuated said first element in said second position engaging said first and said third switches and mechanically operating the first and third switches to their said closed and open positions, respectively; said second control including a second element selectively mountable in a third and a fourth position; when said second element in said third position engaging said second switch and mechanically operating the latter to closed position without operating the remainder of said switches; when said second control is actuated said second element in said fourth position en- References Cited UNITED STATES PATENTS 2,446,299 8/ 1948 Nelson 317-136 X FOREIGN PATENTS 88,033 7/ 1957 Netherlands. 1,155,843 10/1963 Germany.

LEE T. HIX, Primary Examiner.

J. A. SILVERMAN, Assistant Examiner. 

1. A COMBINATION INCLUDING A FIRST AND A SECOND ELECTROMAGNETIC CONTACTOR HAVING A FIRST AND SECOND OPERATING COIL, RESPECTIVELY; ELECTRICAL INTERLOCK MEANS FOR PREVENTING BOTH OF SAID COILS FROM BEING ENERGIZED AT THE SAME TIME; SAID INTERLOCK MEANS COMPRISING A FIRST AND A SECOND NORMALLY OPEN SWITCH; A THIRD AND A FOURTH NORMALLY CLOSED SWITCH; MEANS OPERATING SAID FIRST AND SAID THIRD SWITCHES TO CLOSED AND OPENED POSITIONS, RESPECTIVELY, WHEN SAID FIRST COIL IS ENERGIZED; MEANS OPERATING SAID SECOND AND FOURTH SWITCHES TO CLOSED AND OPEN POSITIONS, RESPECTIVELY, WHEN SAID SECOND COIL IS ENERGIZED; A FIRST ENERGIZING CIRCUIT FOR SAID COIL INCLUDING SAID FIRST COIL, SAID FIRST AND SAID FOURTH SWITCHES CONNECTED IN ELECTRICAL SERIES, WITH EACH OTHER; AND A SECOND ENERGIZING CIRCUIT FOR SAID SECOND COIL INCLUDING SAID SECOND COIL, SAID SECOND AND SAID THIRD SWITCHES CONNECTED IN ELECTRICAL SERIES WITH EACH OTHER. 